Hong Kong's mobile operators are collectively losing about $240 million to $600 million annually, due in part to billing mistakes, customer debts and fraud, according to research by PricewaterhouseCoopers.

After surveying 20 mobile operators from eight countries in the Asia-Pacific region, the consulting firm concluded that up to 30 per cent of their annual revenue was lost through 'leakage' that could be controlled by improved system-monitoring, bill-checking and customer credit controls.

Other contributors to leakage included foregone earnings due to unconnected calls and lost customers because of poor network quality.

Hong Kong's operators are estimated to have an annual revenue leakage rate of between 2 to 5 per cent, the same as the US, PricewaterhouseCoopers' Andrew Watkins said.

The operators' wide range of tariff plans and service options often contributed to the problem.

'If you're looking at an operator with 200 different sales plans, it's very easy for mistakes and inaccuracies to be made,' he said.

PricewaterhouseCoopers found more than half the operators surveyed did not conduct the most basic test to ensure bills were complete.